Not infrequently, the processing and handling of food, and food products, involves the application of oils thereto, or the processing of such foods in close proximity with such oils. In the case of grain handling, for example, the kernels are normally associated with relatively large amounts of finely-divided, dust-producing particles. When suspended in air in particular amounts, such dust is flammable to the point of being violently explosive, and many disasters involving extensive damage to property, as well as the loss of life have been attributed to dust explosions. As a result, extensive precautions are normally taken when handling grains and other finely subdivided foods and food products to remove sources of ignition from the vicinity thereof, and particularly to minimize dusting involving such particles.
Further with respect to such dusting, grain being transported by conveyors is frequently subjected to dust suppression measures, for example, to processing procedures in which the grain is sprayed with atomized oil droplets that display relatively long-lasting, dust-suppressing effects.
While any of a variety of oils can be successfully employed for dust suppression purposes, of equal or possibly greater concern is the problem of foodstuff contamination. In this connection, the Federal Food and Drug Administration, F.D.A., has enacted regulations that prohibit the inclusion of a variety of materials in foodstuffs, either in the form of direct or indirect additives, unless the materials have been specifically approved by the Agency for use with foodstuffs. Most mineral oils fall within such prohibition, and as a consequence, resort is oftentimes had to the use of vegetable oils, for example, soybean oils, in spraying grain for dust-suppression purposes. Although such oils are effective for dust-suppression, they have an unfortunate tendency to become rancid, and thus to adversely affect the quality of the grains with which they are combined. Vegetable oils may also have poor "handling" properties at low temperatures.
In view of the risk of rancidity, so-called "white oils" have also been used for dust suppression. White oils are essentially colorless, odorless, and tasteless mineral oils produced, for example, by the rigorous treatment of light industrial oils with substances such as fuming sulfuric acid, and subsequent extraction with caustic soda. Among other things, the treatment results in the removal of aromatics and olefins from such oils, and the resulting products are relatively non-reactive with many chemicals. Consequently, white oils are widely used in the food, drug, and cosmetic industries due to their non-staining properties, as well as their inertness, and particularly because of their freedom from toxic effects.
White oils have a significant drawback, however, important in certain situations, in that they exhibit relatively high pour points as a result of the substantial amounts of wax contained in the oils. The wax present tends to leave solution when the oils are cooled, resulting in increased viscosity and making the oils difficult to handle, particularly at lower temperatures. While white oils derived from naphthenic mineral oils contain somewhat less wax than those produced from paraffinic materials, even the former oils can contain 10% or more wax, on a weight basis.
For reasons that include a desire to desirably lower their pour points to facilitate low-temperature handling, ordinary mineral oils are typically subjected to dewaxing procedures involving the addition of certain materials, termed dewaxing "aids", to the oils. These assist in the filtration of wax particles precipitated during wax-removing, chilling procedures by reducing the size of the precipitated particles, thus making them easier to filter. Such treatment is not feasible for white oils, however, because of their market applications in the food area, and the fact that such aids have not received approval of the F.D.A., and could at least in part remain in the oil following the wax-removal step.
As a consequence of the difficulty of removing wax from white oils, such oils typically exhibit relatively high pour points compared with ordinary industrial mineral oils. For example, in the case of oils derived from naphthenic stocks, the oils have pour points in the order of about -20.degree. F., compared to about -60.degree. F. for ordinary industrial oils, and in the case of oils processed from paraffinic feed stocks, about +20.degree. F. for the white oils, compared with the pour points of similar industrial oils, which can be as low as about -10.degree. F.
Another approach used in enhancing the low-temperature handling characteristics of ordinary mineral oils involves the use of "flow improvers," or pour point depressants. These include, for example, high molecular weight compositions formed by the alkylation of benzene, or derivatives thereof, by the polymerization of lower molecular weight methacrylates, or by condensation polymerizations involving compounds of various kinds. However, as in the case of dewaxing aids, the use of such materials has ordinarily been avoided insofar as white oils destined for use in association with foodstuffs are concerned, because of the lack of F.D.A. approvals.
Furthermore, because of the costs entailed in the treatment to which the white oils have been subjected during their formation, there is a natural reluctance to separate and discard wax, which if allowed to remain adds to the volume of the oils and, therefore, to the revenues derived from their sale.
Ethylene-vinyl acetate copolymers have in the past been used as pour point depressants in petroleum products other than white oils, and since such copolymers have received certain approvals for use in contact with foodstuffs, having been determined by the F.D.A. to be highly nontoxic, the use of such copolymers with oils intended for human consumption has certain attractions.
However, while such copolymers have been used as pour point depressants in connection with middle distillate petroleum fractions such as diesel fuel, kerosene, heating oils, turbo-jet fuels and the like, they have not been used for, or recognized to be useful for desirably lowering the pour point of mineral oils. To the contrary, various art references including U.S. Pat. Nos. 3,048,479; 3,250,714 and 3,262,873 assert that while the copolymers effectively lower the pour point of middle distillate hydrocarbons, they have no similar effect on mineral-based lubricating oils, and in fact, are ineffective for such purpose. Furthermore, while some ethylene-vinyl acetate copolymers have been used as viscosity index improvers for industrial oils, they have not been used in connection with white oils as pour point depressants.